Fix include guards of files in src/ios.

ios/web/public/test/response_providers/string_response_provider.h

Index: ios/web/public/test/response_providers/string_response_provider.h
diff --git a/ios/web/public/test/response_providers/string_response_provider.h b/ios/web/public/test/response_providers/string_response_provider.h
index c3e985c9071e74d85cfbe91d32278081c96a9df5..e5a0f9e18c9130c5f0ff0652b0031bf913363b47 100644
--- a/ios/web/public/test/response_providers/string_response_provider.h
+++ b/ios/web/public/test/response_providers/string_response_provider.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_
-#define IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_
+#ifndef IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_H_
+#define IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_H_
 
 #include <string>
 
@@ -33,4 +33,4 @@ class StringResponseProvider : public web::DataResponseProvider {
 
 }  // namespace web
 
-#endif  // IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_
+#endif  // IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_STRING_RESPONSE_PROVIDER_H_